1. Field of the Invention
The present invention relates to a grinding wheel used in a grinding machine and the like. More particularly, the present invention relates to a grinding wheel for simultaneously grinding at least two parts of a workpiece.
2. Description of the Prior Art
FIG. 1 shows an example of conventional grinding wheels for simultaneously grinding two parts of a workpiece. The grinding wheel Gc2 is supported on a wheel spindle 8 of a wheel head 2 in a grinding machine 1. The grinding wheel Gc2 includes a sleeve 15, two wheel disks Gca and Gcb supported on the sleeve 15, a spacer 25 located between the wheel disks Gca and Gcb, and a flange 28 for fixing the wheel disks Gca and Gcb on the sleeve 15 by bolts 35. The sleeve 15 has a taper bore 17 formed at the center portion of the grinding wheel Gc2. The taper bore 17 receives a taper portion 9 of the wheel spindle 8, and the grinding wheel Gc2 is engaged on the wheel spindle 8 by a nut 32. A labyrinth seal 34 is formed between the sleeve 15 and the wheel head 2 to prevent grinding fluid from leaking into the wheel head 2. Each of the wheel disks Gca and Gcb consists of a wheel core 11 and an abrasive layer 12 arranged on a circumferential surface of the wheel core 11 for grinding work.
In recent years, a need exists for increase of wheel surface speed of a grinding wheel in order to decrease machining time. However, the grinding wheel Gc2 has a drawback when the wheel spindle 8 is driven at very high speed, e.g., the wheel surface speed is approximately 200 m/s, as described hereinafter. Though the wheel disks Gca and Gcb are balanced, it is difficult that the other parts of the grinding wheel Gc2, i.e., the sleeve 15, the spacer 25, the flange 28 and the like, are sufficiently balanced. The imbalance of the parts increases in accordance with the wheel surface speed of a grinding wheel Gc2. The drawback causes vibration of the wheel disks Gca and Gcb, while the grinding wheel Gc2 is working, making machining accuracy deteriorate.
FIG. 2 shows an example of conventional grinding wheels for grinding work under high wheel surface speed. The grinding wheel is shown in a Japanese Unexamined Patent Publication No. 6-190729. The grinding wheel Gc2 is directly supported on a wheel spindle 38 through a straight bore 27, and clamped with a wheel cap 21 by bolts 29. However, since the grinding wheel Gc2 is for grinding only one part of a workpiece at once, it can not solve the above drawback.